JP2003164737A - Washing method for separation membrane and washing apparatus adapted thereto - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a washing method capable of effectively washing a separation membrane contaminated with organic or inorganic matter in a short time, and a washing apparatus adapted thereto. <P>SOLUTION: In the washing method for the separation membrane contaminated with organic matter and/or inorganic matter, the separation membrane is treated in a washing liquid by an ultra-vibration method and a contaminant is peeled and removed from the surface of the separation membrane to restore the separation capacity of the separation membrane. The washing apparatus for the separation membrane is constituted of a washing tank housing the separation membrane, a device for injecting the washing liquid in the washing tank and an ultra-vibration device arranged to the washing tank. The ultra-vibration device can be constituted of a vibration motor capable of being controlled to a frequency of 20-50 Hz, a vibration plate for accelerating vibration and multistage vibration blades attached to the vibration plate. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a separation membrane cleaning method, and more particularly, to a method for cleaning a separation membrane contaminated with an organic substance or an inorganic substance in wastewater treatment such as sewage, night soil, industrial wastewater, etc. or water purification treatment. Regarding the device.

[0002]

2. Description of the Related Art Separation membranes are used for sewage, night soil, industrial wastewater, etc.
It is widely used for wastewater treatment such as sewage, night soil, industrial wastewater, water treatment for semiconductor industry and pharmaceutical manufacturing industry, and water purification treatment. Separation membranes include ultrafiltration membranes (hereinafter referred to as UF membranes) and microfiltration membranes (hereinafter referred to as MF membranes), COD, BOD and nutrient salts for solid-liquid separation for removal of suspended solids, sludge, aggregates and bacteria. Reverse osmosis membrane (hereinafter R
O membranes) and nanofiltration membranes (hereinafter, NF membranes) are used. Since the RO membrane and the NF membrane have a pore size as small as 1,000 or less in terms of molecular weight cutoff, they are a method of obtaining membrane permeated water under a pressure condition of 200 to 1500 kPa. UF membrane and M among separation membranes
Since the F membrane is easy to operate and manage and clear treated water can be obtained, it has become popular as a solid-liquid separation method instead of gravity separation such as in a settling tank for water purification treatment, night urine treatment, and private small wastewater treatment. There is. Since the UF membrane has a pore size of 1,000 to several hundred thousand in terms of molecular weight cut-off, the UF membrane has 100 to 500 kPa on the object to be treated.
It is a method of applying pressure to pass through a membrane and filtering. MF
The membrane is a system in which it is immersed in a water tank to obtain permeated water under reduced pressure conditions.

However, if any separation membrane is used continuously, contaminants such as polluted water in the treated water adhere to the membrane surface,
The amount of permeated water separated by the separation membrane will decrease.
If the amount of membrane permeate decreases, the planned amount of treated water cannot be treated,
Wastewater treatment becomes difficult. In such a case, cleaning is performed to remove the deposits on the surface of the separation membrane to recover the amount of water permeated through the membrane. In recent years, as a solid-liquid separation membrane in wastewater treatment or water purification treatment, an immersion type M that uses an MF membrane by immersing it in a water tank
F-membrane is widespread. FIG. 4 shows a schematic configuration diagram of a usage pattern of the immersion type MF film. In the biological treated water inflow water, the organic matter in the inflow water is decomposed and removed by the activated sludge in the biological treated water tank. The treated water is discharged from the water tank by a suction pump such as a MONO pump via the MF membrane in the biological treatment water tank.

A practical MF membrane has a pore size of 0.1 to 0.1.
0.4 μm, made of polyethylene, and hollow fiber membranes are widely used. A membrane element is formed by fixing both ends of a plurality of hollow fiber membranes, and a membrane module is formed by further uniting the plurality of membrane elements, and the required number of the membrane modules is installed in the water of the biological reaction water tank.
Alternatively, in order to reduce the power cost for obtaining the permeated water, this MF membrane does not require pressurization conditions, but the inside of the membrane is depressurized by a vacuum pump or a mohno pump, and the permeated water moves from the outside to the inside The general method is to obtain treated water.
The clogging condition of the membrane can be judged by monitoring the pressure difference between the membranes. The differential pressure is generally -1 to -100 kPa (gauge pressure), although it varies depending on the temperature of the water tank and the amount of permeated water.

The increase in the differential pressure is due to the intermembrane clogging due to sludge accumulated on the membrane surface and the membrane contamination with the pores of the membrane clogging, but the former can be eliminated by simple water washing or air washing. The latter is as follows. (1) The separation membrane is taken out of the water tank and washed with high pressure water. However, there is a high possibility that the membrane will be damaged, and the contamination inside the pores cannot be sufficiently removed. (2) Put the separation membrane taken out of the water tank into the washing tank,
A cleaning agent is added, and the cleaning solution is circulated by pump or agitated with air to clean the separation membrane. At present, it is a reliable method of eliminating filtration pressure. However, in such a method, there are problems that the cleaning time is long, the cleaning effect is low, and the cleaning agent is excessive.

[0006]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems of the prior art and is capable of effectively cleaning a separation membrane contaminated with an organic substance or an inorganic substance in a short time. It is an object to provide a method and a device.

[0007]

In order to solve the above problems, in the present invention, in a method for cleaning a separation membrane contaminated with an organic substance and / or an inorganic substance, the separation membrane is treated by a super vibration method in a cleaning liquid. Then, the method for cleaning the separation membrane is characterized in that the contaminants are peeled off from the surface of the separation membrane to recover the separation performance. In the cleaning method, the cleaning liquid may include at least one agent selected from an alkaline agent, a surfactant, an oxidizing agent, and an acid. Further, in the present invention, in a cleaning device for a separation membrane that is membrane-contaminated with an organic substance and / or an inorganic substance, a cleaning tank for containing the separation membrane, a device for injecting a cleaning liquid into the cleaning tank, and a cleaning tank are provided. A cleaning device for a separation membrane, which is characterized by comprising a super vibration device. In the cleaning device, the super vibration device is a vibration motor capable of controlling a frequency of 20 to 50 Hz,
It can be composed of a diaphragm that promotes vibration and multi-stage vibrating blades attached to the diaphragm.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is described in detail below. With the separation membrane of the present invention, sewage, night soil, industrial wastewater, and the like,
It is used for wastewater treatment such as sewage, night soil, industrial wastewater, water treatment and water purification, and solid-liquid separation for removing suspended solids, sludge, aggregates and bacteria, and removal of pollutants such as COD, BOD and nutrient salts. RO membrane, NF membrane, UF membrane,
It is an MF film. The film deposit in the present invention is not particularly limited, but may be a metal compound such as a metal hydroxide, a metal oxide, a metal carbonate, a metal bicarbonate, or a metal sulfide, or slime, which is an aggregate of organic substances and microorganisms. Is a general term for substances that exist on the surface of the membrane or inside the pores of the membrane and reduce the membrane separation performance.

The present invention is a method for recovering the performance of a separation membrane contaminated with an organic substance or an inorganic substance, which is a cleaning method for removing contaminants from the surface of the separation membrane by a super vibration method.
FIG. 5 shows a schematic configuration diagram of the super vibration cleaning device. In the super vibration cleaning method, a violent flow is generated at a low frequency to vigorously stir the cleaning liquid, so that vibration and flow simultaneously occur, violent three-dimensional turbulent agitation occurs, and vibration of the vibration motor enters the liquid. The vibration is transmitted vertically to the shaft and transmitted to the multi-stage vibrating blade. By attaching a soft vibrating blade to a stiff diaphragm to generate flutter like a fan, a stronger flow is generated to remove contaminants from the surface of the separation membrane. The cleaning effect is high because not only vibration but also stirring accompanied by flow occurs. Due to the synergistic effect of the two physical forces, it is possible to clean the details of the object to be cleaned.

An excellent cleaning effect can be exhibited even in the case where cleaning is extremely difficult, such as in the case of minute holes in which the cleaning liquid does not easily penetrate, contaminants that are strongly adhered, and separation membranes that are the objects to be cleaned are in close contact with each other. The removed contaminants are made into fine particles, stabilized in the cleaning liquid, and do not reattach to the object to be cleaned. Further, the structure of the super-vibration cleaning device is simple and space-saving, and it can be applied to the shape of the separation membrane such as large and small. 1 to 3
FIG. 1 shows a schematic configuration diagram of the cleaning apparatus of the present invention. The separation membrane is
As shown in FIG. 1, the case where the super-vibration cleaning device is carried in to the place where the separation membrane is installed and the cleaning is performed at that place without removing the separation membrane, and the case where the separation membrane is removed as shown in FIGS. 2 and 3 There is a method of cleaning the membrane by putting it in a cleaning water tank equipped with a super-vibration cleaning device, and the present invention can be used in any case.
For each module that includes a separation membrane, frame, and piping,
Alternatively, the separation membrane itself can be washed with a super vibration washing device.

As a liquid for immersing the separation membrane, pure water, industrial water, or various kinds of easily available treated water can be used. When cleaning is performed with the separation membrane installed, the liquid at the installation location, such as activated sludge or aeration tank mixed liquid, corresponds to the cleaning liquid. Further, the cleaning liquid used in the present invention may be a cleaning liquid containing at least one chemical agent selected from an alkaline agent, a surfactant, an oxidizing agent and an acid. By combining the super-vibration cleaning method and a cleaning liquid containing at least one agent selected from an alkaline agent, a surfactant, an oxidizing agent and an acid, the contaminants can be more effectively peeled off from the surface of the separation membrane. By using the cleaning agent in combination, the cleaning agent can be supplied even to minute holes and firmly attached contaminants, and the cleaning effect can be enhanced. Alkali agents are caustic soda, oxidizing agents are chlorine-based oxidizing agents such as sodium hypochlorite, hydrogen peroxide, acids are organic acids such as phosphoric acid, oxalic acid and citric acid, and surfactants are sodium lauryl sulfate. Such as industrial detergents and household detergents.

In general, if the contaminant is an inorganic substance, an acid is used. If the contaminant is an organic substance, an oxidizing agent alone, an alkaline agent alone, a surfactant alone, or a mixture thereof is used. Further, after washing with an alkali agent or a surfactant, washing with an acid may be performed, and vice versa. It can be arbitrarily selected depending on the contaminant. It goes without saying that the washing effect is high if the washing temperature is high as long as the separation membrane is not deformed. The washing temperature is preferably 20 to 40 ° C. The present invention is a cleaning device for a separation membrane, which comprises a cleaning tank equipped with a cleaning liquid injection device and a super vibration device. The cleaning liquid injection device includes a cleaning agent storage tank and a cleaning liquid injection pump.
The super vibration device is composed of a cleaning tank, a vibration motor, a vibration plate that promotes vibration, a multi-stage vibration blade, and the like. Optimal cleaning strength can be obtained by controlling the frequency of the vibration motor to 20 to 50 Hz through the inverter.

[0013]

EXAMPLES The present invention will be specifically described below with reference to examples. Example 1 Water treatment was carried out using a membrane separation activated sludge treatment facility at a food service center having a planned water amount of 40 m ³ / day as shown in FIG.
The equipment has a BOD load of 0.2 kg / kg day and MLSS1.
0 g / l, raw water BOD 200 mg / l, membrane permeation flux 0.2 m ³ / m ² / day, MF membrane (pore size 0.1 μm, made of polyethylene), membrane area 200 m ² . One module is 10 m ² and 20 modules are installed in the membrane separation activated sludge treatment water tank. Approximately 5 months after washing the MF membrane of this equipment with a washing solution of 5% sodium hydroxide and 5% sodium hypochlorite, the pressure difference between the membranes became 60 kPa and the amount of permeated water decreased. The membrane module (1 module was 1 m in length and 70 cm in width) in which the MF membrane was incorporated was removed, and a cleaning test was performed using the apparatus shown in FIGS. 2 and 3.

The super-vibration device was a vibration motor of 1 kW, and vibrated a single vibration plate having 10 vibration blades having a width of 20 cm and a total length of 60 cm, which were attached at intervals of 10 cm.
In the super vibration device, 1 m ³ of tap water having a water temperature of 25 ° C. was placed in the installed washing water tank, and one module having a membrane area of 10 m ² per module was immersed in this for 10 to 60 minutes for washing. Further, using a cleaning solution of 5% caustic soda and 5% sodium hypochlorite, the cleaning solution was pumped and circulated for about 10 minutes for cleaning. The module after washing was attached to a membrane separation activated sludge treatment facility to investigate the performance of the separation membrane. Table 1 shows the test results of Example 1.
A high cleaning effect was observed even with super vibration alone. further,
By adding the cleaning agent, it was possible to suppress an increase in the differential pressure of the MF membrane.

[0015]

[Table 1]

Example 2 One of the modules incorporated in the membrane-separated activated sludge treatment facility of Example 1 was surrounded by a vinyl chloride resin plate, and the super-vibration device of Example 1 was installed in the module. The cleaning test was conducted with the above apparatus. Table 2 shows the test results of Example 2. Without removing the membrane module of the biological treatment tank, it can be washed by lifting it, and its effect is high. Even when the membrane separation activated sludge treatment water tank was washed using an ultra-vibration device, no trouble occurred in the subsequent membrane separation activated sludge treatment.

[0017]

[Table 2]

[0018]

The effects of the present invention are as follows. (1) A high cleaning effect can be obtained with a small amount of cleaning agent or in a short period of time. (2) The details of the separation membrane can be washed, and the membrane separation performance can be maintained for a long time. (3) Contaminants do not redeposit and there is no recontamination of the membrane. (4) The membrane can be cleaned at that location without removing it.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an example of a cleaning apparatus of the present invention.

FIG. 2 is a schematic configuration diagram showing another example of the cleaning apparatus of the present invention.

FIG. 3 is a schematic configuration diagram showing another example of the cleaning apparatus of the present invention.

FIG. 4 is a schematic configuration diagram of a biological treatment water tank using an immersion type MF membrane.

FIG. 5 is a schematic configuration diagram of a super vibration cleaning device.

Claims (4)

[Claims] 1. A method for cleaning a separation membrane contaminated with an organic substance and / or an inorganic substance, wherein the separation membrane is treated by a super vibration method in a cleaning liquid to remove contaminants from the surface of the separation membrane to separate the membrane. A method for cleaning a separation membrane, which comprises recovering 2. The method for cleaning a separation membrane according to claim 1, wherein the cleaning liquid contains at least one agent selected from an alkaline agent, a surfactant, an oxidizing agent, and an acid. 3. A cleaning device for a separation membrane, which is contaminated with an organic substance and / or an inorganic substance, in a cleaning tank for accommodating the separation membrane, a device for injecting a cleaning liquid into the cleaning tank, and a super tank provided in the cleaning tank. A cleaning device for a separation membrane, which comprises a vibrating device. 4. The super vibration device has a frequency of 20 to 50H.
4. The separation membrane cleaning apparatus according to claim 3, comprising a vibration motor that can be controlled to z, a vibration plate that promotes vibration, and a multistage vibration blade that is attached to the vibration plate.